ALT 
sented in our flora by its variety rigidissimus, one of the most common 
of Arizona forms and extending to southwestern Texas, and the variety 
centralis, also an Arizona form. This same pectinatus type is rep- 
resented at the east by cespitosus, the most eastern of our CEREI, 
reaching the Canadian and Arkansas Rivers in Indian Territory, and 
apparently not occurring west of the Pecos, its Mexican extension 
being in the States east of Chihuahua. 
The purple-flowered nonpectinate species, six in number, range from 
the Salt Lake Desert of Utah on the north to the eastern slopes of the 
Californian Sierras and the middle Rio Grande on the south, their Mex- 
ican connections extending from Lower California to Coahuila. But 
one of them (mojavensis) is peculiar to our flora, occurring in the desert 
regions of southeastern California, Arizona, and southern Utah, Four 
of the species reach Texas: dubius in the Rio Grande bottoms from 
El Paso downward, with no western extension, but with a Mexican 
extension into Chihuahua and Coahuila; enneacanthus all along the 
Lower Rio Grande and to El Paso, with a similar Mexican extension, 
but reaching Arizona on the west; stramineus, common in the Pecos and 
El Paso region, extending down the Rio Grande, west to Arizona, and 
south into Coahuila; and fendleri, a Sonoran and Chihuahuan type, 
which stretches through Arizona to Utah and east to southwestern 
Texas. The dominant species of the group, however, engelmanni, is 
far western in its distribution, extending from Lower California and 
Sonora along the eastern slopes of the Californian Sierras and through 
Arizona and Nevada to the Salt Lake Desert of Utah. Two strong 
varieties of this species are peculiar to our flora: variegatus, occurring 
with the species within our borders, and chrysocentrus, confined to the 
deserts of southeastern California. 
The searlet-tlowered nonpectinate species, eight in number, contain 
five peculiar to our flora, but these five are species of no great abun- 
dance, and one of them (hexaedrus) has never been rediscovered. The 
three remaining species, which are the doininant ones, are all common to 
the Chihuahua region, and extend from the El Paso region to southern 
California. Of the five species restricted to the United States, gona 
canthus is the most northern and the most removed from the Mexican 
flora, occurring in southern Colorado and northern New Mexico; 
heraedrus is the least known, having been found but once, and then 
near Zuni, New Mexico; paucispinus inhabits the narrow belt between 
the San Pedro and Pecos rivers of Texas, a range, however, which . 
specimens recently received from Durango, Colorado, will modify; triglo- 
chidiatus ranges from east of the Pecos in Texas northward into New 
Mexico; while octacanthus has the most extended range, reaching from 
the El Paso and Pecos region of Texas northwestward through New 
Mexico into Utah. The three species of wide range and Mexican repre- 
sentation are: aggregatus, extending from southern Colorado through 
eastern Arizona and southwestern Texas to San Luis Potosi; roemeri, 
